Pesticides and Toxicology: A Century of Environmental Health is the first detailed historical examination of the development of the art and science of environmental risk assessment. This study reveals how health scientists, industry scientists, science writers, government regulators and legislators responded to threats to environmental health throughout the twentieth century. At several key nodes during the twentieth century, scientists and popular science writers united to inspire protective legislation. Each of these episodes revealed rapid increase in new chemicals, toxicological methodologies, popular awareness, and legislative activity. While the chemical industry continued to generate literally thousands of new chemicals, particularly insecticides, scientists and legislators struggled to respond with appropriate safety standards. The development of the chemicals continues to proceed faster than the methods of analysis and regulation. Such challenges gave rise to the evolution of environmental risk assessment, which has become the dominant paradigm in the analysis of environmental quality and health. My research seeks to answer several key questions: How did the methodologies of toxicology evolve alongside the development and widespread use of new chemical insecticides? How did toxicology coalesce into formal academic programs, a society, and a discipline? How did science writers depict threats to environmental health in ways that raised popular awareness and legislative concern? How did corporations, represented by the chemical and pesticides trade organizations, attempt to address (or dismiss) the concerns of consumers and their representatives? What was the role of the new study of toxicology in Rachel Carson's Silent Spring? How did government regulators and legislators employ toxicology in the development of policies regarding pesticides? Finally, how did environmental risk assessment draw on the methodologies of toxicology? Thus, in answering these questions, Pesticides and Toxicology provides insights into the evolution of environmental health and its many facets: the institutions, corporations, government organizations, as well as popular perceptions of toxicology, environmental risk assessment, and environmental health policy. Project Narrative Pesticides and Toxicology: A Century of Environmental Health has considerable significance to public health in that it will explore the foundations of the closely related discipline of environmental health. This is a story that will appeal to historians of public health, medicine, and science. Beyond the expected academic readership, this study should interest the wider community of people who wish to understand the role of pesticides, toxicology, and environmental risk assessment in the evolution of environmental health, activism, and policy.